This invention pertains to a firearm of a type employing a barrel loosely coupled with respect to a frame unit, such as a receiver of a pistol, and including a slide member having sights and disposed about the barrel where the slide member is also coupled to the receiver unit for movement relative to the receiver unit and barrel between recoil and battery positions. This invention is particularly useful in conjunction with accurizing a firearm wherein all of the parts fit relatively loosely so that the parts will be relatively widely interchangeable.
While the present invention is described in conjunction with the Colt .45 caliber semi-automatic pistol, it is to be understood that the invention is not to be considered as limited solely to one particular weapon.
As is known, the Colt .45 pistol is and has been one of the most reliable, useful handguns ever manufactured. The Colt .45 handgun has been widely used in all of the military services of this country where it is employed primarily as a side arm for purposes of providing the wearer with a weapon able to develop great impact upon targets which are quite close to the person carrying such weapon. In addition, this particular firearm has been virtually failsafe and foolproof by virtue of its simplicity of construction and design, its few parts, and its ease of assembly and disassembly for cleaning and repair.
The foregoing weapon was manufactured with interchangeability of parts as an important feature and, accordingly, most of the parts fit relatively loosely.
Obviously, the fact that the sights are carried by the slide and not by the barrel of the weapon make accuracy at long range very difficult, if not impossible, to achieve in view of the foregoing considerations (primarily the looseness with which the weapon is generally assembled).
Heretofore, due to the general attractiveness of the Colt .45 weapon, a number of attempts have been made to improve its accuracy and these typically have involved simply tightening of the parts. Some attempts involve use of tightly fitted pieces at the muzzle of the weapon.
It is readily evident, however, that the tighter that a barrel bushing is made to fit between the muzzle end of the barrel and slide, the greater will be the chances that the slide will stick or "freeze" when it should otherwise be returning freely under recoil. Thus, there is imposed an obvious limit to the degree of tightness which can be achieved between the barrel and slide at the muzzle of the weapon.
Another source of inaccuracy is to be found in the relatively loosely coupled mounting of the breech end of the barrel with respect to the receiver. This looseness in the region of the slide stop pin (in the Colt .45) tends to cause the breech end of the barrel to reposition itself at different positions for each well of the gun with little or no consistency. For example, the barrel extension lug 17 is disposed in a wall 20 of receiver 11 and moves between advanced and retracted positions so as to require sufficient clearance to permit such movements. This clearance permits the breech end of the barrel to move from side to side within well 20.
On additional source of looseness if found between the side edge of the barrel hood 54 and an interior surface of the slide.
Yet another source of inaccuracy is to be found in the looseness required to be permitted in the sliding coupling formed between the slide and receiver where a land-and-groove connection is made.